The present invention relates to electric rotary machines such as electric motors and electric generators, and a method for producing the electric rotary machines.
Conventionally, electric rotary machines such as electric motors, for example, have been manufactured as units. For this reason, an indoor unit of an air conditioner, for example, requires a space for receiving a separate motor such as an alternating-current induction motor to drive a cross-flow fan in the indoor unit. As a result, the indoor unit is apt to be of a large size. In other words, separate electric rotary machines cause apparatuses for accommodating the rotary machines to be largesized.
Recently, direct current (DC) brushless motors have been adopted to reduce the size of apparatuses. An apparatus adopting a DC brushless motor is disclosed in the Japanese Patent Application Laid-open Publication No. 64-41696. In the apparatus, a generally cup-shaped casing for a rotor in the DC brushless motor is connected to a side plate of a fan rotor of a cross-flow fan, and a permanent magnet which is fitted along an inner peripheral surface of the casing surrounds a stator.
Conventionally, the permanent magnet is produced by the following method. First, a molded piece of a desired shape is made by sintering a magnetic material such as ferrite. Then, the molded piece is finished so that it has a shape to fit the inner circumferential surface of the casing. The finished molded piece is then placed in the casing.
The molded piece of such magnetic material is very hard and fragile. For this reason, generally, an abrasive finishing is applied to the molded piece as a finishing method. In this case, the production cost becomes high. In addition, it is not easy to make holes in the molded piece for fixing the molded piece to the casing. Therefore, in order to mount the molded piece to the casing, separate articles to help the fixing are required, or an adhesive-assembly is done. This makes the assembly operation complicated and troublesome.